**   *  Definitions of sqlite3_io_methods objects for all locking
**      methods plus "finder" functions for each locking method.
**   *  sqlite3_vfs method implementations.
**   *  Locking primitives for the proxy uber-locking-method. (MacOSX only)
**   *  Definitions of sqlite3_vfs objects for all locking methods
**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
**
** $Id: os_unix.c,v 1.247 2009/03/28 23:47:11 drh Exp $
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX              /* This file is used on unix only */

/*
** There are various methods for file locking used for concurrency
** control:
................................................................................
        pFile->lastErrno = tErrno;
      }
      goto end_unlock;
    }
  }
  if( locktype==NO_LOCK ){
    struct unixOpenCnt *pOpen;


    /* Decrement the shared lock counter.  Release the lock using an
    ** OS call only when all threads in this same process have released
    ** the lock.
    */
    pLock->cnt--;
    if( pLock->cnt==0 ){
................................................................................
        pLock->locktype = NO_LOCK;
      }else{
        int tErrno = errno;
        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
        if( IS_LOCK_ERROR(rc) ){
          pFile->lastErrno = tErrno;
        }
        pLock->cnt = 1;
        pLock->locktype = NO_LOCK;
        pFile->locktype = NO_LOCK;
        goto end_unlock;
      }
    }

    /* Decrement the count of locks against this same file.  When the
    ** count reaches zero, close any other file descriptors whose close
    ** was deferred because of outstanding locks.
    */
    if( rc==SQLITE_OK ){
      pOpen = pFile->pOpen;
      pOpen->nLock--;
      assert( pOpen->nLock>=0 );
      if( pOpen->nLock==0 && pOpen->nPending>0 ){
        int i;
        for(i=0; i<pOpen->nPending; i++){
          /* close pending fds, but if closing fails don't free the array
          ** assign -1 to the successfully closed descriptors and record the
          ** error.  The next attempt to unlock will try again. */
          if( pOpen->aPending[i] < 0 ) continue;
          if( close(pOpen->aPending[i]) ){
            pFile->lastErrno = errno;
            rc = SQLITE_IOERR_CLOSE;
          }else{
            pOpen->aPending[i] = -1;
          }
        }
        if( rc==SQLITE_OK ){
          sqlite3_free(pOpen->aPending);
          pOpen->nPending = 0;
          pOpen->aPending = 0;
        }
      }


    }
  }
	
end_unlock:
  unixLeaveMutex();
  if( rc==SQLITE_OK ) pFile->locktype = locktype;
  return rc;

**   *  Definitions of sqlite3_io_methods objects for all locking
**      methods plus "finder" functions for each locking method.
**   *  sqlite3_vfs method implementations.
**   *  Locking primitives for the proxy uber-locking-method. (MacOSX only)
**   *  Definitions of sqlite3_vfs objects for all locking methods
**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
**
** $Id: os_unix.c,v 1.248 2009/03/30 07:39:35 danielk1977 Exp $
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX              /* This file is used on unix only */

/*
** There are various methods for file locking used for concurrency
** control:
................................................................................
        pFile->lastErrno = tErrno;
      }
      goto end_unlock;
    }
  }
  if( locktype==NO_LOCK ){
    struct unixOpenCnt *pOpen;
    int rc2 = SQLITE_OK;

    /* Decrement the shared lock counter.  Release the lock using an
    ** OS call only when all threads in this same process have released
    ** the lock.
    */
    pLock->cnt--;
    if( pLock->cnt==0 ){
................................................................................
        pLock->locktype = NO_LOCK;
      }else{
        int tErrno = errno;
        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
        if( IS_LOCK_ERROR(rc) ){
          pFile->lastErrno = tErrno;
        }

        pLock->locktype = NO_LOCK;
        pFile->locktype = NO_LOCK;

      }
    }

    /* Decrement the count of locks against this same file.  When the
    ** count reaches zero, close any other file descriptors whose close
    ** was deferred because of outstanding locks.
    */

    pOpen = pFile->pOpen;
    pOpen->nLock--;
    assert( pOpen->nLock>=0 );
    if( pOpen->nLock==0 && pOpen->nPending>0 ){
      int i;
      for(i=0; i<pOpen->nPending; i++){
        /* close pending fds, but if closing fails don't free the array
        ** assign -1 to the successfully closed descriptors and record the
        ** error.  The next attempt to unlock will try again. */
        if( pOpen->aPending[i] < 0 ) continue;
        if( close(pOpen->aPending[i]) ){
          pFile->lastErrno = errno;
          rc2 = SQLITE_IOERR_CLOSE;
        }else{
          pOpen->aPending[i] = -1;
        }
      }
      if( rc2==SQLITE_OK ){
        sqlite3_free(pOpen->aPending);
        pOpen->nPending = 0;
        pOpen->aPending = 0;
      }
    }
    if( rc==SQLITE_OK ){
      rc = rc2;
    }
  }
	
end_unlock:
  unixLeaveMutex();
  if( rc==SQLITE_OK ) pFile->locktype = locktype;
  return rc;